How can I change duration of Sprint to three weeks ?
By the way, I must admit that this is one of the best and most intuitive tools that I have ever seen for SCRUM... Thank you so much for giving this to the society of Scrum Practitioners.

How can I change duration of Sprint to three weeks ?
By the way, I must admit that this is one of the best and most intuitive tools that I have ever seen for SCRUM… Thank you so much for giving this to the society of Scrum Practitioners.

Wow! Thanks for the great compliment Ramesh. I am just happy if a few people find the application useful :)

The Sprint start and end dates can be set to whatever you choose i.e. if you want a Sprint duration of 3 weeks, just select an end date that is three weeks later than the start date. The "Duration" drop-down and the "Calculate" button are really there to make it quicker to work out the end date if you are using more these more common Sprint durations. I kept it simple and most importantly flexible because in my experience the Sprint duration depends on all kinds of factors and may well change as a Scrum Team matures.